An LTE (long term evolution) project is an evolution of 3G and is a transition between 3G technology and 4G technology. The LTE is a global 3.9G standard, which improves and enhances an air access technology of 3G. In addition, the LTE improves performance of cell edge users, increases a cell capacity, and reduces a system delay, and employs an OFDM (orthogonal frequency division multiplexing) and an MIMO (multiple input multiple output). The LTE is a unique standard for radio network evolution of the LTE.
During transmission of downlink service data of the LTE, multiple UEs (User Equipment, user terminal, briefly referred to as user) in one cell multiplextime frequency resources dynamically, where time frequency resources occupied by each UE are controlled by a PDCCH (physical downlink control channel) corresponding to the UE. When a transmitting end transmits a control signal to UEs, the transmitting end needs to perform scrambling on PDCCHs of the UEs.
In the prior art, in LTE Rel-10 and earlier releases, scrambling sequences used to perform scrambling on PDCCHs of UEs are extracted from a long sequence. Specifically, each PDCCH includes at least one CCE (control channel element), where a data length of each CCE is 36 REs (resource element); because a modulation mode of the PDDCH in LTE Rel-10 and earlier releases is a QPSK (quadrature phase shift keying), in which each RE is 2 bits, a scrambling sequence that needs to be extracted by each CCE is 72 bits long; because scrambling sequences that need to be extracted by all CCEs are in the same length, an start position of a corresponding scrambling sequence that needs to be extracted by a current CCE can be determined by merely knowing how many CCEs have already extracted a scrambling sequence.
In LTE Rel-11, because CoMP (coordinated multi-point), MU-MIMO (multiple user-multiple input multiple output) enhancement and the like are considered, the PDCCH capacity becomes a bottleneck to the increase of system throughput. Therefore, further enhancement of the PDCCH capacity is considered in the 3GPP (the 3rd Generation Partnership Project). A newly added PDCCH channel is called an ePDCCH (enhanced physical downlink control channel), and each ePDCCH includes at least one eCCE (enhanced control channel element). In LTE Rel-11, the modulation mode of the ePDCCH is no longer only the QPSK, and may further be a 16 QAM modulation and a 64QAM modulation. In this way, a data length of each eCCE in the ePDCCH is no longer fixed, and therefore the length of a scrambling sequence that needs to be extracted is no longer always 72 bits. When a kth eCCE in the ePDCCH uses the QPSK modulation mode, the length of a scrambling sequence that needs to be extracted by the kth eCCE is 2×NeCCEkRE bits; when the kth eCCE uses the 16 QAM (quadrature amplitude modulation), the length of the scrambling sequence is 4×NeCCEkRE when the kth eCCE uses the 64QAM, the length of the scrambling sequence is 6×NeCCEkRE bits. In this case, an start position of a corresponding scrambling sequence that needs to be extracted by a current eCCE cannot be computed by merely knowing how many eCCEs have extracted a scrambling sequence, which results in that the current eCCE cannot extract a scrambling sequence. In this way, scrambling and descrambling cannot be performed on the ePDCCH in multiple modulation modes.